The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
A manual transmission drivetrain includes an internal combustion engine (ICE), a clutch and a manual transmission. The clutch engages with a flywheel on the ICE and transfers torque output of the engine to the manual transmission. Torque transfer from the ICE to the transmission is interrupted when a vehicle operator manually shifts between gears of the transmission. During a gear shift event, the clutch is disengaged (i.e. the ICE is disengaged from the transmission), a desired gear is manually selected, and the clutch is reengaged. Disengagement of the ICE from the transmission can negatively affect fuel economy and vehicle acceleration.
An automatic transmission drivetrain may include an internal combustion engine (ICE), a torque converter and an automatic transmission with planetary gear sets. The ICE provides output torque to the torque converter. The torque converter transfers torque from the ICE to the automatic transmission based on engine speed. The planetary gear sets include sun, carrier and ring gears that include input, output and stationary operating states. Different gear ratios are selected by adjusting the operating state of each of the planetary gears in the planetary gear sets. An automatic transmission drivetrain provides uninterrupted torque transfer from the ICE to an output shaft of the automatic transmission. Typically, complex logic based approaches are used to control operating states of the planetary gears.
A dual-clutch transmission (DCT) drivetrain includes an ICE and a DCT (or semi-automatic transmission). The DCT includes two clutches, inner and outer transmission shafts, and two gear sets with respective gear shafts and/or lay shafts. As an example, the inner transmission shaft may be associated with a first gear set and controlled using a first clutch. The outer transmission shaft may be associated with a second gear set and controlled using a second clutch. The first gear set may include first, third, and seventh gears. The second gear set may include second, fourth, sixth, and reverse gears. By using two transmission shafts, a DCT drivetrain can provide uninterrupted torque transfer between the ICE and an output shaft of the DCT during gear shifts. This decreases shift times and improves fuel economy.